1. Field of the Invention
The present invention relates to a centralized control system that carries out centralized control of a system having a large number of sensors and actuators, such as a printer and a copy machine, and particularly to a communication centralized control system and a communication centralized control method for control of communication between one master device and plural slave devices via a bus.
2. Description of the Related Art
FIG. 1 is a diagram showing the basic configuration of a bus network system in which bidirectional communication is carried out between a single master device and plural slaves.
In this bus network system 1, one master device 2 and plural slave devices 3-1 to 3-X are connected by a communication bus 4.
Bidirectional communication is carried out between the master device 2 and the plural slave devices 3-1 to 3-X via the communication bus 4.
In some cases, in the bus network system 1, the number of lines of the communication network is small and transmission/reception data are communicated by serial transmission.
In such a system, as shown in FIG. 2, the master device 2 carries out operation called polling, in which the master device 2 performs data exchange with the respective slave devices 3-1 to 3-X in turn.
In such polling operation, one of the slave devices 3-1 to 3-X often carries out interrupt operation of performing emergency data exchange.
In the case of executing such interrupt processing, as shown in FIG. 3, normal polling communication is temporarily stopped and interrupt communication is carried out.
Serial data transmission processing techniques are disclosed in Japanese Patent Laid-open No. 2005-142872 and Japanese Patent No. 3496501.